1. Field of the Invention
The present invention disclosed in the present specification relates to a film formation method and a method for manufacturing a light-emitting element.
2. Description of the Related Art
Light-emitting elements using an organic compound as a light emitter, which have features such as thinness, lightweight, fast response, and direct current low voltage driving, have been applied to next-generation flat panel displays.
It is said that, as for a light-emitting mechanism of a light-emitting element, an EL layer (also referred to as a light-emitting layer) is sandwiched between a pair of electrodes and voltage is applied, and thus electrons injected from a cathode and holes injected from an anode are recombined in an emission center of the EL layer to form molecular excitons, and the molecular excitons release energy when returning to a ground state; thus, light is emitted.
As one of methods for forming an EL layer, a technique is developed. In that technique, an organic material which is an EL material is uniformly deposited on a substrate that is referred to as a donor, and the donor on which the organic material is deposited is placed over/under an another substrate and irradiated with a laser beam, and an organic thin film (an EL layer of a light-emitting element) in a region irradiated with the laser beam is transferred to the another substrate (see References 1 to 5). As such a technique of laser transfer, laser-induced pattern-wise sublimation (LIPS), laser-induced thermal imaging (LITI) (see Reference 6), and radiation induced sublimation transfer (RIST) are proposed.
Further, it is known that, onto one surface of metal foil, short pulse energy which is absorbed and causes vaporization and plasmatization of the metal, for example light energy including laser light, is applied; thus, a jet is generated by a sudden expansion of a metal gas and a shock wave is generated on the other surface of the metal foil (see Patent Document 7).
In Patent Document 7, the following is known. That is, short pulse energy such as a Q-switch laser beam emitted to metal foil induces ablation, and, as a result of its reaction, a shock wave is generated in the metal foil. The shock wave is reflected on the other surface of the metal foil as an expansion wave; thus, the metal foil is deformed at extremely high speed, and micro particles on the metal foil are blasted off at extremely high speed.
[Reference]
    Reference 1: Japanese Translation of PCT International Application No. 2007-504621    Reference 2: Japanese Published Patent Application No. 2003-223991    Reference 3: Japanese Published Patent Application No. 2003-308974    Reference 4: Japanese Published Patent Application No. 2003-197372    Reference 5: Japanese Published Patent Application No. H10-208881    Reference 6: Japanese Published Patent Application No. 2006-5328    Reference 7: Japanese Published Patent Application No. 2002-272460
There are problems in a method for forming an EL layer by heating and transferring an organic material which is an EL material in that an edge portion of the EL layer has a small thickness and the organic material is not uniformly transferred.